Cardiovascular diseases appear in various types of lesions including aneurysm, atherosclerosis, and stenosis. These diseases are caused by pathological changes of normal parts with an influence of blood flow, and although the diseases would be fatal in many cases depending on their growth stages, it is extremely difficult to treat them because such a treatment may risk the patient's life span. For understanding these refractory cardiovascular diseases, it is beneficial to apply advanced engineering technology including fluid analysis and structural analysis, in addition to the fundamental medical approach of studying underlying pathology.
For example, cerebral aneurysm is an angiopathy where a part of a cerebral artery wall protrudes outward, forming a shape similar to a balloon, and there are an increasing number of clinical cases of accidentally discovering an un-ruptured aneurysm while conducting a brain image diagnosis. A cerebral aneurysm appears due to the vulnerability of the cerebral artery wall, altering a part of the wall to develop a lump which is fragile due to the lack of the tunica media, and it is most likely a cause of subarachnoid hemorrhage because many cases of cerebral aneurysm tend to appear in the subarachnoid space. Therefore, a cerebral aneurysm giving a high potential of rupture needs to be treated proactively by conducting a proper surgical treatment such as a stent treatment.
However, the probability of the actual rupture of cerebral aneurysms is reported to be less than 1% annually for the size 10 mm or less; thus, considering the risk of post-surgical complication, preventive treatment would not be necessarily appropriate in some cases, and consequently rather than relying on surgical treatment alone, it is required to determine a subject to be treated by judging an aneurysm at a greater probability of rupture. For this reason, there have been research conducted on methods for diagnosing a cerebral aneurysm based on its size and shape, the family record, the blood pressure, and the habit of cigarette smoking, and other factors of the patient. Nevertheless, these indicators are not deterministic factors of the diagnosis, and developing a more effective diagnostic method is demanded.
Japanese Patent Application Publication No. 2010-207531 discloses MRI equipment that may diagnose the risk of aneurysmal rupture by analyzing the viscous force of fluid that exerts on the inner wall of cerebral aneurysm, i.e., by analyzing the magnitude of wall shear stress of the fluid. However, regarding the correlation between the magnitude of the wall shear stress and the growth of aneurysm there are several controversial arguments where the diagnostic results are contradicting each other. A first theory is the High Wall Shear Stress (WSS) theory which explains that cerebral aneurysm grows due to an appearance of an endothelial cell fault once the wall shear stress exceeds a certain threshold value which results in the infiltration of migratory cells, leading to reduce the mechanical strength of the aneurysm wall. A second theory is the Low WSS theory which explains that once the wall shear stress drops below a certain threshold value, platelets or white blood cells that adhere to the endothelial cells lower the endothelial function, resulting in the reduction of the mechanical strength of the aneurysm wall. Because those theories have explanations opposite to each other, the magnitude of the wall shear stress is not a direct measure of determining the growth and rupture of the aneurysm.
There are other attempts to determine the rupturing risk by investigating the magnitude of the wall shear stress, e.g., a method for analyzing the blood flow either experimentally or computationally to extract the wall shear stress from medical images acquired by MRI or CT. However, as pointed out above, there is no conclusive correlation between the magnitude of the wall shear stress and the risk of rupture, and furthermore, the method of using medical images medical image is a methodology that is only based on the morphology of a vascular lumen, and thus provides no interpretation of the flow itself. This is because the observation of medical images fails to allow us to obtain pathological information of cellular conditions and morphological information of aneurysmal wall thickness, which change locally on the aneurysm wall, while the magnitude of the wall shear stress itself also varies locally on the aneurysm wall.
Considering the above issues, the present invention has been researched and developed, aiming the purpose that provides a method for determining a possible appearance of lesion in a target vascular site and its potential growth based upon a diagnostic result of the blood flow characteristics of the targeted blood vessel, and furthermore, and predicting the effect of treatment, a system thereof, and an accompanied software program.